The invention relates to a method and relevant devices for controlling the unloading operations in sorting plants of the kind employed where considerable numbers of items are to be treated, e.g. in post offices, in mail order companies and the like.
These are plants where the different functions are carried out and synchronized by a central computer that controls the course of the operations.
A standard plant of this type comprises a fixed path along which run a plurality of carriages or "units" on which the items to be sorted are placed. The items are automatically unloaded when the relevant carriage passes before a determined collecting area when the item is being introduced in the apparatus, by means of computer controlled and actuated devices.
Plants of this kind are described in the following Italian patents and/or applications by the same Applicant: Italian Pat. No. 1 152 067; Italian Pat. No. 1 151 648; Italian utility Model No. 180 770; Italian App. Nos. 22476 C/83, 21310 B/85, 24227 B/85, 28859 A/81, 21774 B/82, 23110 A/84. 22264 A/84 and 20779 A/85. Each item is coded by an operator and placed on the sorting path in loading stations the number of which varies as a function of the amount of items to be sorted.
The path is developed to have various shapes and sizes. A train of units occupies either the whole path or just a part thereof.
The units are set in motion--according to methods known in the prior art--for instance by means of a continuous driving chain (when the path is substantially a rectilinear one) or by means of electric motors set on board the units themselves and fed by power bars parallel to the path (when the path is a carrousel).
The items, conveyed by the units, reach the collecting stations where The items, conveyed they are unloaded. The unloading is effected by means of movable belts that constitute the loading surface of the units. At the moment of unloading, the unit belt is actuated by sending a voltage signal to the relevant motor by means of bus bars in order to enable the drive control of only that belt-unit which is involved in the unloading. Bus bars are sectioned to correspond to the unloading station and are thus different from power bars for actually powering the motor. The unloading may take place at either side of the sorting path by simply reversing the direction of rotation of the belt, whose direction of rotation is perpendicular to the direction of unit motion.